Gas injection to leach precipitation process



July 22, 1969 J. R. DENNY ET AL 3,457,065

GAS INJECTION TO LEACH PRECIPITATION PROCESS Filed Dec. 28, 1965 3Sheets-Sheet 1 INVENTORS .7. 19. 064/40 0.5. yolsyunswmwy July 22, 1969J. R. DENNY ET AL 3,457,065

GAS INJECTION TO LEACH PRECIPITATION PROCESS Filed Dec. 28, 1965 I5Sheets-Sheet 2 INVENTORS .714- oewuv I a. .r. KRIJNAMJWAMV y 1969 J. R.DENNY ET AL 3,457,065

GAS INJECTION TO LEACH PRECIPITATION PROCESS Filed D80 28, 1965 3Sheets-Sheet 3 INVENTORS .7. e. Dew/v7 0.x. Ak/J'A/A/AJh/AMV UnitedStates Patent 3,457,065 GAS INJECTION TO LEACH PRECIPITATION PROCESSJere Robert Denny, New York, N.Y., and Deenahalli S.

Krishnaswamy, Kelly Lake, Minn., assignors to Kennecott CopperCorporation Filed Dec. 28, 1965, Ser. No. 516,953 Int. Cl. C22b 3/00,3/02 US. Cl. 75109 6 Claims ABSTRACT OF THE DISCLOSURE This inventionrelates to processes and apparatus for precipitating metals from aqueoussolutions. More particularly, the invention relates to processes andapparatus for the recovery of cement or precipitate copper from pregnantleaching solutions containing copper values, by passing the pregnantleaching solutions into contact with iron, for replacement of the coppervalues in the solutions by iron values.

In recent years, increasing attention has been turned to the productionof cement or precipitate copper, to augment the recovery of copper frommines by conventional mining techniques. Devices have been proposed forincreasing the efficiency of the precipitation reaction.

For example, United States Patent 3,154,411, issued Oct. 27, 1964,discloses one type of reaction device, that may aptly be described as aprecipitation cone, where the precipitant is finely divided iron. Thisprecipitant is maintained in dynamic suspension in the pregnant leachingsolution, which is injected into the cone at its apex.

Another type of reaction device that could be employed would be acolumnar device in which the precipitant metal is maintained as a loosemass within a generally upright column, and the pregnant leachingsolution is passed upwardly through the mass of precipitant metal. Suchdevices are disclosed, for example, in United States Patent 597,372,issued Jan. 11, 1898.

Still another type of device, that is being employed for carrying outprecipitation reactions, makes use of a vessel that is nested withinanother vessel. The inner vessel is generally conical in shape, with itsapex directed downwardly, and with its upper rim spaced from theinterior surface of the outer vessel, to provide a gap. This gap iscovered with a screen. The precipitant metal is placed within the innervessel, and may be heaped up over the screen. A piping system isarranged to direct pregnant solution into the interior of the innervessel, for flow upwardly through the precipitant metal. An overflowcollection trough is disposed adjacent the upper rim of the outervessel, to carry off stripped or barren liquid. The precipitate copper.can pass through the screen to accumulate in the space between the twovessels, from which it can be drained off as desired. Percipitatingdevices of this type are described, for example, in the co-pendingUnited States patent application of Zimmerley and Malouf, Ser. No.319,302, filed Oct. 28, 1963.

One object of the present invention is to provide a new, improved,practical method for improving the efliciency and effectiveness of metalprecipitation reactions. A related object of the invention is to providepractical apparatus for carrying out the method of the invention.

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Another object of the invention is to provide a relatively simple,inexpensive, and effective way for improving the performance of existingmetal precipitation processes and devices.

A more specific object of the invention is to provide a relativelysimple, inexpensive technique for improving the recovery of precipitatecopper.

Other objects of the invention will be apparent hereinafter from thespecification and from the recital of the appended claims.

In the drawings:

FIG. 1 is a fragmentary part side elevation, part axial section, ofprecipitation apparatus that is constructed in accordance with onepreferred embodiment of this invention;

FIG. 2 is a top plan view thereof, partly broken away, on an enlargedscale;

FIG. 3 is a fragmentary section, taken on the line 3-3 of FIG. 2,looking in the direction of the arrows;

FIG. 4 is a transverse section through one of the secondary fluid supplylines, showing two of the injection jets, on an enlarged scale, and

FIG. 5 is a graphic demonstration of the effect of secondary fluidinjection upon copper recovery, in accordance with one embodiment of thepresent invention.

Referring now in detail to the drawings by numerals of reference, thenumeral 10 denotes a structural framework that is used to support aprecipitation device that is constructed in accordance with onepreferred embodiment of this invention. This structural frameworksupports the device but is not essential otherwise to its operation, andconsequently is omitted from other views.

A pad 11 is disposed within the framework 10 to provide a base for thedevice. The device is formed with an outer vessel that is generallyindicated by the numeral 12. This outer vessel has a wall 14 thatengages against the base 11 at its lower end, and is formed with ahorizontal section that increases upwardly, so that it has a generallyconical or truncated conical shape. At its upper end, the outer vesselis formed with a generally cylindrical upward extension 15. Thisextension 15 is formed with an outwardly extending apron 16 and adownwardly depending skirt 18, for structural purposes. A trough 19 ismounted within the cylindrical extension to provide an overflow toreceive barren liquid. A discharge line 20 is disposed to communicatewith the trough 19.

A second generally conical wall 21 is also mounted on the base 11,within the outer wall 14. This inner wall 21 also is generally in theshape of a truncated cone, and is generally in parallelism with theouter wall 14. The inner wall 21 is uniformly spaced from the outerwall, and is shorter than the outer wall, thereby providing a gapbetween the upper rim of the inner wall 21, and the confronting surfaceof the outer wall 14. In effect, this provides a vessel within a vessel.

A heavy gauge stainless steel mesh 24 is secured to extend between theupper rim of the inner wall 21 and a confronting but higher portion ofthe surface of the outer wall 14. While stainless steel is a preferredmaterial for this mesh, any other relatively inert, strong mesh materialmay be employed.

In the space between the two vessels, at their lower ends, a slopingplatform 25 is disposed, for a Purpose to be described presently. Thisplatform is sloped toward a discharge pipe 26, for permitting materialsto be discharged from the space between the two vessels.

To supply pregnant leaching solution to the interior of the innervessel, a manifold line 28 is extended upwardly through the base 11, toproject into the interior of the inner vessel, generally axiallythereof. Within the inner vessel, the manifold line communicates with agenerally upright stub extension 29, that is closed at its upper end.

It also communicates with a plurality of upwardly and outwardlyextending lines 30. These lines 30 are interconnected at their upperends respectively to a manifold ring 31, that is disposed just below theupper end of the inner wall 21. A plurality of short nipples 32 aredisposed at spaced intervals along the lengths, respectively, of theupright stub extension 29, the lines 30, and the manifold ring 31. Allof these nipples are disposed to direct pregnant leaching fluid towardthe interior of the inner vessel, except those on the upright stubextension 29, which are directed generally radially outwardly andupwardly.

To supply secondary fluid to the device, a second manifold line 34 isconnected through the base 11, and it communicates, in the interior ofthe inner vessel, with a ring 35 that is disposed on the surface of thebase 11, at the lower end of the inner wall 21. This bottom ring 35communicates through a horizontally-extending line 36 with an upwardlydirected line 38 that is engaged against and extends along the innersurface of the outer wall 14. An intermediate ring 39 is disposed withinthe inner vessel, in a central region between the lower and upper endsof the inner vessel. This intermediate ring 39 communicates through aline 40 with the generally upright line 38. An upper ring 41 is disposedbeneath the mesh 24, and also communicates with the upright line 38.

The bottom ring 35, the intermediate ring 39, and the upper ring 41, areeach provided with a plurality of nipples 32 that permit discharge intothe device. These nipples are directed either generally radiallyinwardly or are inclined somewhat upwardly.

FIGURE 4 is a transverse section on the intermediate ring 39, to showthe manner in which the nipples may be arranged on that ring.

To place the device in operation, a load of scrap iron is dropped intothe device, through its open upper end. Shredded tin can scrap, producedby burning tin cans to remove the tin coating, the label, any lacquercoating, solder from the seams, and any remainder of the originalcontents of the can, is a satisfactory kind of iron scrap for use in thedevice. The manifold line 28 is then connected to a source of pregnantleaching solution containing copper values. This pregnant solution ispumped through the manifold line 28 under sufficient pressure so that itfills the upright stub extension 29, the lines 30, and the manifold ring31, and sprays out through their respective nipples 32 ratherforcefully.

The pregnant leaching solution gradually rises within the vessels untilit reaches the mesh 24. At this point, it overflows, until it fills thespace between the inner wall 21 and the outer wall 14. It then continuesto rise until it overflows into the trough 19, and is carried away Theinjection of pregnant solution is maintained at a suflicient rate sothat the particles of precipitate copper are carried up out the innervessel and into the quiescent zone above the inner vessel. There, theprecipitate copper settles, and falls through the mesh 24 into the spacebetween the inner wall 21 and outer wall 14. A heavy sludge ofprecipitate copper in spent leaching solution accumulates on theinclined platform 25, and may be removed through the discharge line 26.

In accordance with the present invention, the manifold line 34 is nowsupplied with compressed air. The air flows into the device through thejets on the bottom ring 35, the intermediate ring 39, and the upper ring41. The volume of air entering the device preferably is controlled byadjustment of a valve. The pressure at the supply may therefore have anyvalue that is suflicient to deliver the desired volume of air into thedevice through the adjusting valve. Supply pressures of p.s.i. andhigher have been employed successfully.

The injection of air into the device creates substantial turbulence. Thearea of greatest turbulence is within the inner cone. However, since theair rises up through the device until it escapes at the surface of theleaching solution, there is agitation throughout the device. However,the air injection does not eliminate the relatively quiescent zone, sothat precipitate copper continues to fall through the mesh screen 24 andaccumulate between the inner and outer vessels.

The results that are obtained, as compared to the results obtainedwithout the injection of a secondary fluid such as air, are quitesurprising. The relative improvement obtained, for a given device,depends upon such parameters as type of precipitant metal employed, rateof pregnant solution input, concentration of the pregnant solution,operating temperature, and the like. However, the injection of asecondary fluid gives consistent improvement in the operation in manyways. For example, the rate of throughput can be increasedsubstantially, with improvements of several hundred percent having beenobserved and not being unusual. The recovery of copper is increasedseveral percent, with improvements on the order of about up to about 20%having been commonly observed.

In order to demonstrate the improvement that was obtained in theperformance of a reaction device, through the use of the presentinvention, a precipitation cone was operated with and without airinjection, with other operating variables being held substantiallyconstant. First, the cone was operated in accordance with prior artpractice, without air injection. The operting data of interest issummarized below in Table I.

TABLE I.CONE PERFORMANCE, WITHOUT AIR INJECTION Pregnant solution,Barren solution,

lbs/1,000 gals. lbs/1,000 gals.

Operating Feed Recovery shift rate, g.p.m. Cu Fe Fe Cu Fe Fe?" of CuAverages l, 954 3. 85 1. 68 56. 4

through the discharge line 20. As the pregnant leaching solution rises,the copper values are replaced and precipitate copper is formed, as isconventional.

With normal operating variables held substantially constant, the conewas then operated with air injection. The observed results aresummarized in Table II.

TABLE II.CONE PERFORMANCE, WITH AIR INJECTION Pregnant solution, Barrensolution,

lbs/1,000 gals. lbs/1,000 gals.

Feed Recovery rate, g.p.m. Cu Fe" Fe*** Cu Fe Fe*"* of Cu Averages 1,914 3. 0. U 7|). 4'-

In both tables, the percentage recovery of copper is calculated foraverage copper content of both pregnant solution and barren solution.

During operating shifts 5 and 6, air Was injected into the cone, whichhad substantially the configuration illustrated in the drawings, onlythrough the bottom ring and the intermediate ring. During shifts 7 and8, the volume of air was adjusted to be substantially less than thevolume used during shifts 5 and 6.

As the results in these tables demonstrate, the recovery of copper issubstantially improved by the injection of air.

The effect of employing different amounts of injected air was observedduring another series of demonstrations of the invention. The observeddata is summarized in Table III below.

TABLE IIL-EFFECT OF CHANGING THE AIR VOLUME INJECTED Lbs. Cir/1,000gals.

Ratio of water to Operating air, by Pregnant Barren Percent Cu testvolume solution solution recovery The ratio of water to air, by volume,is in terms of ambient conditions of temperature and pressure.

As the data in Table III demonstrates, at the particular feed rateemployed, increasing copper recoveries were obtained as the amount ofinjected air Was increased. The optimum amount of air to be employed, inany particular piece of equipment, with any particular kind of pregnantleaching solution, would have to be determined by experimentation.

Improvements in performance have been obtained not only by using air,but also by using other injected fluids. For example, nitrogen andoxygen have been successfully employed. In some cases, the use of barrenleaching solution as a secondary fluid gives successful results in theform of improved performance.

While the reason for the improved performance is not clear, it appearsthat the injection of a secondary fluid enhances the contact between thepregnant solution and the precipitant metal. Possibly the injection of asecondary fluid effects a scouring action on the precipitant metal, toremove the precipitate copper that might otherwise slow down thereaction rate. Also, it is possible that the injection of the secondaryfluid increases turbulence within the device and thus accelerates therate of contact between the precipitant metal and the pregnant leachingsolution. Whatever the reason, as the data presented demonstrates,improved operating performance is obtained.

While the invention has been disclosed herein by reference to thedetails of a preferred embodiment thereof,

it is to be understood that such disclosure is intended in anillustrative, rather than a limiting sense, and it is contemplated thatvarious modifications in the technique of the invention will readilyoccur to those skilled in the art, within thespirit of the invention andthe scope of the appended claims. For example, while the invention hasbeen described herein with specific references to the application of theinvention to a precipitating cone in which shredded tin cans have beenemployed as the precipitant metal, it is equally applicable toprecipitating devices such as cones, columns, and the like, where otherprecipitant metals are employed, such as, for example, a precipitatingcone employing powdered sponge iron as the precipitant.

What is claimed is:

1. A method of precipitating particles of a desired metal from apregnant solution containing values thereof, comprising:

maintaining a generally upright body of a loose mass of a precipitantmetal for stripping desired metal values from a pregnant solutionthereof, in the form of a particulate precipitate;

forcefully applying pregnant solution to said body of precipitant metal;

directing the solution generally upwardly through said mass ofprecipitant metal, and

simultaneously forcefully directing a different fluid at varying levelsagainst said loose mass of precipitant metal to enhance the contactbetween the pregnant solution and the precipitant metal.

2. A method in accordance with claim 1 wherein the step of directing adifferent fluid against the mass of precipitant metal comprisesforcefully directing a gas in a plurality of separate streams againstsaid mass of precipitant metal.

3. A method in accordance with claim 2 wherein said gas is air.

4. A method in accordance with claim 2 wherein said gas comprisesoxygen.

5. A method in accordance with claim 1 wherein the step of directing adifferent fluid against said mass of precipitant metal comprisesdirecting an aqueous relatively barren fluid against said mass ofprecipitant metal.

6. A method in accordance with claim 3 wherein the pregnant solutioncontains copper value and the precipitant metal is iron.

References Cited UNITED STATES PATENTS 3,333,953 8/1967 Zimmerley et al-l09 3,154,411 10/1964 Back et a1 75109 689,835 12/1901 Waterbury 75109788,443 4/1905 Waterbury 75109 L. DEWAYNE RUTLEDGE, Primary ExaminerTERRY R. FRYE, Assistant Examiner

